Extended flute milling cutters are well known in the industry. They enable using one or more sets of cutting inserts, each set comprising several consecutive cutting inserts arranged at the periphery of the cutter, axially overlapping each other, in order to form a long peripheral effective cutting edge for milling, for example, a deep shoulder whose depth is larger than the length of a side cutting edge of a single cutting insert. In the circumferential direction of the milling cutter, each cutting insert is considered to belong to a circumferential row (“row”), each row typically having at least as many cutting inserts as the number of sets.
As a result of a growing demand for high productivity cutting tools, many extended flute milling cutters available in the market are provided with internal cooling ducts in order to supply cooling medium to the cutting inserts. Some milling cutters are provided with coolant holes adjacent each of the cutting inserts mounted therein in order to effectively supply cooling medium to the active cutting edge of each of the cutting inserts.
In some applications, for example, when milling a shallow shoulder whose depth is less then the length of the extended flute milling cutter, not all the rows of the cutting inserts are used. For example, if the milling cutter is provided with five rows of cutting inserts, it may be that only the first two axially forwardmost rows are active whilst the three axially rearwardmost rows are not active, i.e., do not participate in the cutting process. In such a case, the axially rearwardmost rows of cutting inserts are unnecessarily cooled. As a result, the coolant volumetric flow rate is ineffectively used since it could have been directed in its entirety to the active rows only. This leads, of course, to unnecessary operation costs which could be saved.
A solution to this deficiency, as suggested by several tools manufacturers, is producing the cooling holes with threads. Thus, if it is required to avoid using several rows of cutting inserts, the respective cooling holes are plugged with screws that are threadingly engaged with the threads of the cooling holes.
Even though the outcome of such a solution is cooling only the active rows of cutting inserts, this solution may not be practical since it may require threadingly engaging or disengaging a large number of very small screws each time a change of the cutting depth is required, a task that is substantially time consuming.